Liquid loading is a widely encountered phenomenon in natural oil and gas well production, and in wet gas and hydrocarbon transmission pipelines in the oil and gas industry. In natural gas or oil production, as a reservoir is depleted over the production cycle, decreasing formation pressure and gas velocity causes the production rate of gas or oil to decline. As a result, produced liquid might not be lifted out of the well and may accumulate in the wellbore and production tubing. The hydrostatic pressure associated with the liquid column will in turn hinder production and in some cases, even cause production to cease. The low flow-rate in operating gas or hydrocarbon pipelines can lead to significant liquid accumulation as well due to the action of gravity or vapor condensation coupled with the undulating trajectory of the gas transport pipeline. The liquid accumulation not only restricts production or transportation, but also leads to undesired outcomes such as increased corrosion to the asset (e.g., pipeline or production equipment). Effective removal of the liquid maximizes production and transmission efficiency and reduces the risk of corrosion.
Various methods are used to minimize liquid loading, including the use of velocity strings, intermitters, additional compressors, and liquid foaming agents.
Liquid foaming agents, also known as foamers, are commonly used to aid in unloading liquid from transport pipelines and from natural gas and oil wells where naturally occurring gas or injected gas is present. Foamers can be applied either by batch treatment or continuous application. With the addition of foamer to the wellbore where the loading liquids are present, foam is generated with the agitation from the gas flow. The surface tension and fluid density of the foam are lower than that of the liquids so the lighter foam, whose bubble film holds the liquids, is more easily lifted by the low gas flow rate. In oil well production, foamers are also used in conjunction with a gas lift system to enhance oil production. Foamers are also used in conjunction with a lift gas to enhance oil recovery from the oil well. In gas pipelines, foamers are used to introduce foam to sweep the liquid accumulation.
US 2006/0128990 describes a method of treating a gas well comprising a chloride free amphoteric surfactant. U.S. Pat. No. 7,122,509 provides a method of preparing a foamer composition having an anionic surfactant and a neutralizing amine. US 2005/0137114 discloses an aqueous foaming composition comprising at least one anionic surfactant, cationic surfactant and at least one zwitterionic compound. WO 02/092963 and US 2007/0079963 disclose a method for recovering oil from a gas-lifted oil well using a lift gas and a foaming surfactant which consists of nonionic surfactants, anionic surfactants, betaines, and siloxanes. U.S. Pat. No. 8,551,925 describes quaternized imidazoline-based foamers for enhancing oil and gas production and inhibiting corrosion. US patent application US 2012/0279715 discloses applying quaternary foamers to relieve liquid loading and mitigate corrosion in oil and gas production and transport.
While such foamers contribute significantly to deliquifying gas and oil wells, there remains a need for other cost-effective foamers which could provide superior performance in unloading hydrocarbon, water or mixtures thereof from wells and transport pipelines.